Nina Koistinen was arrested and booked into the Maricopa County Jail on one count of first-degree murder after her 6-day-old baby daughter, Maya Koistinen, was found not breathing, said Sgt. Tommy Thompson, Phoenix Police Department.

Officers responded to a residence near 56th Street and Thunderbird Road on April 8, 2013 where they discovered baby Maya not breathing, Thompson said. The baby was taken to the hospital where she was pronounced dead.

The mother initially told police that she fell asleep while nursing the baby and the father discovered the baby under her arms, according to Thompson.

Detectives interviewed Nina Koistinen on April 25, 2013 where she "admitted to purposely smothering the baby to death," according to police documents.

Koistinen told detectives she smothered the baby because she thought she had too many children already and she was jealous of the attention her husband was giving to the baby, according to court documents.

She is the mother of nine, including baby Maya.

"She's been the greatest mother," said Brad Koistinen, the suspect's husband.

In court on Friday he defended his wife saying she suffered from several mental disorders including bi-polar disorder and depression.

"She has never once hurt any of our kids," he added.

Child Protective Services has opened at least one investigation into the mother.

According to court paperwork, CPS has recorded statements made by Nina claiming she wanted to smother some of her children. She also made similar statements about wanting her children to go to heaven after she got into an accident that appeared to be intentional.

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